[TW-1410] Adaptive format for displaying dates as tersely as possible

_Jeremy John Reeder on 2014-09-04T18:12:21Z says:_

In a task report, it would be very nice to have date formats which adapt automatically based on the proximity of the date to the current time. For example, I'd like a format which displays each date in the least verbose way possible. For example, when the day is today, T17 is a sufficient way to say today at 17:00. This could enable us to get the data that we need without overly verbose reports. Here's an example report:

```
ID Due Description
* - ---------------- -------------
1 T17 Submit report
2 2014-09-05 Wash laundry
3 2014-09-05T11:30 Buy pickles
```